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The KMTNet (Korea Microlensing Telescope Network) was completed on October 2nd in 2015. There are three 1.6 m telescopes in Chile (CTIO), Australia (SSO) and South Africa (SAAO). The field of view of the CCD camera is 2 degree × 2 degree. We are monitoring and observing the bulge region for 24-hour continuous observations using the KMTNet telescopes. I present the characteristics of CCD camera and telescope, and the status of observation programs. We are still developing CCD cameras to accurate photometry. From the KMTNet data, we can obtain accurate 24-hour continuous time-series data for many variable stars. [ABSTRACT FROM AUTHOR]

Time series observations for the 41 RR Lyrae stars in Kepler's fields were carried out in 2010 to 2013 using a number of meter class (or smaller) telescopes. These telescopes include the 1-m and 41-cm telescopes of Lulin Observatory (LOT and SLT respectively, Taiwan), the 81-cm telescope of Tenagra-II Observatory (TNG, Arizona, USA), the 1-m telescope at the Mt. Lemmon Optical Astronomy Observatory (LOAO, Arizona, USA), the 1.8-m and 15-cm telescopes at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea), and the 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO, Korea). All of these telescopes were equipped with commercial available CCD imagers, and the observations were done in standard BVRI filters. Photometric calibration of the RR Lyrae light curves was done with standard stars listed in Landolt standard stars [1]. Observations of selected Landolt standard stars (centered on SA 107-456 & SA 110-232) in Johnson-Kron-Cousins BVRI filters, spanning three distinct airmasses, were done with the 81-cm Tenagra II telescope on 25 June 2011. Raw imaging data were reduced with IRAF in the same manner as in the case of the RR Lyrae, and astrometric calibrated with astrometry.net [2].We calibrated BVRI magnitudes for 40 RR Lyrae stars. [ABSTRACT FROM AUTHOR]

The variable star population in and around the LMC globular cluster NGC 2210 has been studied using 270 new B, V CCD images taken with the CTIO 0.9-m telescope on seven nights in Dec’07, seven nights in Jan’08, and nine nights in Dec’08. The search for variable stars and photometry has been completed. A total of 56 variable stars were identified, including 30 RRab stars (at least three of which are Blazhko variables), nine RRc stars, two certain (and 2 candidate) RRd stars, and 13 other non-RR Lyrae variable stars. [ABSTRACT FROM AUTHOR]

High-resolution spectroscopic observations have been made for 32 of the 34 candidate SX Phe stars identified in the Kepler field by Balona & Nemec (2012). All available long-and short-cadence Q0-Q17 Kepler photometry has been analyzed for the 34 candidates. Radial velocities (RVs), space motions (U, V, W), projected rotation velocities (υ sin i), spectral types, and atmospheric characteristics (Teff, log g, [M/H], υmic, etc.) were derived from ~ 160 spectra taken with the ESPaDOnS spectrograph on the Canada-France-Hawaii 3.6-m telescope and with the ARCES spectrograph on the Apache Point Observatory 3.5-m telescope. Two thirds of the stars are fast rotators with υ sin i > 50 km/s, including four stars with υ sin i > 200 km/s. Three of the stars have (negative) RVs > 250 km/s and retrograde space motions, and seven stars have total space motions > 400 km/s. All the spectroscopically measured SX Phe candidates have positions in a Toomre diagram that are consistent with being bona fide halo and thick-disk stars. Although several stars show a marked metal weakness, the mean [Fe/H] of the sample is near 0.0 dex (σ ~ 0.25 dex), which is considerably more metal-rich than is normally expected for a sample of Pop. II stars. Observed pulsation frequency modulations and optical time delays suggest that at least eight of the SX Phe stars are in binary systems, some of which show significant RV variations. Six of the time-delay binaries have secondary masses ranging from 0.05 to 0.70 M☉ and orbital periods in the range 9 to 1570 days. Another star appears to be an ellipsoidal variable with a 2.3-day orbital period; and two other systems have orbital periods longer than the ~ 4-year sampling interval of the Kepler data. [ABSTRACT FROM AUTHOR]